Used to describe a person who is unpleasant, abhorrent, obnoxious, or just not doing what you want them to. First used by Eric the 'Alfwit, of Lobotomy Racing, to describe Bernie Blackman, and other such jerks. Can be used lightly, (1), if a friend is being gross, or more seriously, (2), if someone is causing shivers-down-the-spine, gagging disgust. Can also be used on someone who is causing annoyance or aggravation of any kind, but no discomfort (3).

2) Perv teacher: *walks up behind (girl) student and places hand on shoulder, attempting to create gape in front of shirt and thus get an eyeful, under the guise of checking that they're working and not writing notes*
Sooo... What are you working on today?
Student: *holds shirt closed with hands*
Modesty, bumgerm.

3) Teacher: I am brilliant. Mozart is brilliant. Elevator music pwns... (continues his self-indulgent rant about the brilliance of things that he likes and the general suckiness of everyone who does not agree with him)
Student: Ugh. Bumgerm much?